1. Field of the Invention
The present invention relates to a method for moving image reproduction, and more particularly to a method for moving image reproduction for the purpose of display of NTSC format image data obtained as 32 pull-down from an image of a movie as an non-interlaced image on a display.
2. Related Art
In order to view a moving image recorded on a projection film such as a movie on a home-type television, it is necessary to convert the images of each frame of the projection film to, for example, an image signal of the NTSC system (National Television System Committee color system) such as used in television broadcasting and the like. A film is usually played back as a continuous moving image by projecting 24 frames of images each second. For this reason, for a movie the image is updated every 1/24 second. In contrast to this, in the NTSC system there are 30 frames displayed every 1 second, and the images of each frame are divided up into even-numbered fields and odd-numbered fields and updated every 1/60 second. For this reason, if a frame of a movie is simply converted to an NTSC format on a one-to-one basis, the recorded time will be shortened by 20% in comparison with the normal amount of time.
For example, there are 144 frames (24 frames×60 seconds) in 1 minute of a movie, and if these are assigned as is to 30 frames/second in the NTSC system, the movie would end in 48 seconds, and the movement would be too fast. For this reason, in the case of converting a movie to an NTSC system film, as shown in FIGS. 6 (a) and (b), a method of conversion known as 32 pull-down, in which 1 frame of a move is converted alternately to 2 fields or 3 fields. This is done because if 5 fields are generated for 2 frames, 24 frames will become exactly 60 fields. FIG. 6 (a) shows a movie comprising image frames Film 01 to Film 05 which are updated every 1/24 second, and FIG. 6 (b) shows an NTSC system movie updated every 1/60 second, divided into even and odd fields.
With increasing usage of personal computers in recent years, discs onto which NTSC formatted movies have been recorded as image data are being played back and viewed using personal computers. In this case, because the display of the personal computer displays in a non-interlaced manner, in the case of using a personal computer to play back a disc intended for playback in the NTSC format, such as a DVD-Video disc, image data for 1 frame is generated from odd and even field data, and the moving image is played back by updating the image every 1/30 second.
In the case in which the original image is a movie, however, because the recorded image data is subjected to 32 pull-down processing, if this image data is converted to a non-interlaced display for each frame individually, the following problems occur.
The first problem is that, as shown at Frame 03 and Frame 04 in FIG. 6(c), there is a shift that appears between fields in the played back picture. The second problem is that, as show in FIG. 6(a) to FIG. 6(c), after Film 01 is displayed as Frame 01, Film 02, until the time that Film 02 is displayed as Frame 02, there is a time period of 1/30 second, whereas after Film 02 is displayed as Frame 02, until Film 04 is displayed as Frame 05 there is a time period of 3/30, although there should be a time period of 2/30 second, meaning that the image is not played back with uniform time intervals.
Accordingly, it is an object of the present invention to provide an apparatus and a method for playing back NTSC format image data recorded with 32 pull-down processing, such as a movie, as a moving image without time shift on a non-interlaced type display